1. Technical Field of the Invention
The present invention relates to engine control devices for controlling internal combustion engines and, more particularly, to an engine control system and an engine control method having a function to detect or calculate a combustible component quantity of intake air of an internal combustion engine.
2. Description of the Related Art
In the related art, attempts have heretofore been made to provide an internal combustion engine having a combustion chamber supplied with intake air containing fresh air and fuel components such as evaporative fuel delivered from a fuel tank or blow-by gas ejecting from a crankcase. As such fuel components increase in intake air drawn to a combustion chamber of the engine, these fuel components results in an increase in a total volume of fuel in an air/fuel mixture to be prepared in the combustion chamber and, thus, the air/fuel mixture becomes too rich, causing a deterioration in control accuracy of an output of the engine. Thus, a need arises to correctly detect or calculate a combustible component quantity of intake air drawn to the combustion engine and take appropriate measures against such defective control accuracy.
To address such an issue, an internal combustion engine has been proposed with a structure having a canister connected between a fuel tank and an intake air passage through a purge passage incorporating a purge control valve (see, for example, Japanese Unexamined Patent Publication No. 5-288107). The opening degree of the purge control valve is controlled to vary a flow passage area between the fuel tank and the intake air passage. With such a structure, a concentration of evaporative gas in intake air is detected on the basis of the amount of displacement of the purge control valve operated in feedback control of an air/fuel mixture at stages in fore and aft movements of the purge control valve.
With such a control device, however, it is hard to detect a combustible component quantity of intake air resulting from combustible components contained in blow-by gas ejected from the crankcase. The presence of the combustible components in intake air is caused by an increase of combustible components coming from the combustion chamber into the crankcase. As the combustible components increase in the crankcase in volume, the amount of combustible components increases in intake air of the engine. In addition, the presence of the combustible components causes a dilution of engine oil in the crankcase, resulting in a lubrication defect between a cylinder wall surface of the engine and a piston. Thus, a need arises detecting or calculating a combustible component quantity of intake air resulting from the combustible components in the crankcase.